Airway stenosis (or “airway narrowing”) is a medical condition that occurs when some portion of a patient's airway becomes narrowed or constricted, thus making breathing difficult. A stenosis may occur in any part of the airway—i.e., larynx, trachea, bronchi or a combination (laryngotracheal or tracheobronchial stenosis)—in adults or children, and due to any of several different causes. By far the most common airway stenoses (approximately 95%) are acquired, meaning the patient is not born with the condition, and the most common cause of airway stenosis is trauma caused by intubation (a tube placed in the airway for ventilation/breathing assistance in a patient who cannot breathe). Intubation for prolonged periods of time may traumatize the airway, causing scar tissue formation that forms the stenosis. Sometimes the cause of stenosis is unknown, such as in idiopathic subglottic stenosis. Managing airway stenosis is one of the most challenging problems for an ENT (ear, nose and throat) surgeon.
Subglottic stenosis is one form of airway stenosis that occurs in the larynx, below the glottis (the area of the larynx around the vocal cords). The disorder can be either congenital or acquired and can affect both adults and children. Acquired subglottic stenosis is the most common acquired anomaly of the larynx in children and the most common abnormality requiring tracheotomy in children younger than one year. To correct subglottic stenosis, the lumen of the cricoid area is expanded to increase airflow during breathing. Surgical correction of subglottic stenosis has been performed with various techniques over the years.
Therapies for treating airway stenosis range from endoscopic treatments, such as dilation and laser resection, to open procedures, such as laryngotracheal reconstruction. In one technique, a series of rigid dilators of increasing diameter are pushed down the airway, gradually expanding the constriction but also applying unwanted shear forces to the airway. More recently, balloon catheters have been used to perform airway dilation. One of the benefits of balloon dilation over rigid dilation is the application of radial force versus shear force, which reduces the risk of mucosal trauma. Also, depending on the balloon catheter used, a surgeon has greater confidence in the precise amount of pressure needed to dilate the stenotic region of the airway.
Today, most airway dilations using balloon catheters are performed using angioplasty balloon catheters and peripheral balloon catheters, which are designed for dilating narrowed blood vessels. These balloon catheters have several limitations when used for dilating an airway stenosis. First, because these balloons catheters are not specifically designed to be used in the airway, the dimensions of existing balloons may not be optimized for ease of use within pediatric and/or adult airways. Second, current balloon catheters are generally not sized to allow convenient visualization of airway balloon dilation using an endoscope (e.g., laryngoscope or bronchoscope), and in fact in some cases it is not possible to view the airway dilation procedure using an endoscope. Third, balloon catheters used for vascular procedures are generally very long and floppy, which may make them difficult to advance into a constriction in an airway and which may lead to a tendency of the balloons of such catheters to slip or “watermelon seed” out of the constriction when inflated. In general, it can be challenging to position a currently available balloon catheter in a desired location for an airway procedure, dilate the balloon without having it slip out of the narrowed portion of the airway, and visualize the procedure.
Therefore, it would be desirable to have an airway stenosis balloon dilation system that is designed to be used in an airway, rather than in a blood vessel or some other anatomical structure. Ideally, such a system would have dimensions configured for use in an airway, would allow for visualization of at least part of an airway dilation procedure and/or of the system during the procedure, and could be advanced into (and maintained within) an airway constriction more easily than currently available balloon catheters. At least some of these objectives are addressed by the embodiments described in this application.